Which element has the smallest ionic radius among the following cations?
For isoelectronic cations (Li+, Be²⁺, B³⁺, C⁴⁺, all with 2 electrons), radius decreases with increasing nuclear charge. B³⁺ (Z=5) is smaller than Li+ (Z=3), Be²⁺ (Z=4), and C⁴⁺ (Z=6).
Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Periodic Trends - Atomic Radii Ionic Radii and Ionization Enthalpy